JP2008524659A - Indexed optical fiber connector - Google Patents

Abstract

A high performance connector for an optical fiber includes a cylindrical ceramic or metal ferrule attached to a structure. This structure is positioned on a non-plastic (metal system) base member to form a fiber holder. This overall cylindrical structure generally includes a small passage along its central axis to hold the optical fiber. The entire structure is mounted in a non-plastic housing that includes an opening that protrudes from a ceramic ferrule at one end. A cylindrical spring integrally formed with the ferrule support structure and interacting with the inner surface of the surrounding structure via the second piece of the cylindrical structure is a ceramic ferrule facing outward from the opening in the housing. Energize. The housing includes a metal leaf spring located on one side, which can be manually operated and used to lock the connector to the associated receptacle. The connector has very stable optical performance in a wide range of (thermal and mechanical) environments because the structural components (metal and / or ceramic) are made of non-plastic. High performance optical connectors also incorporate the ability to directly inspect sensitive internal components (springs, internal metal or ceramic components) or remove cylindrical fiber holders to be cleaned. In addition, the cylindrical structure comprises “tuning” means that remove the effect of fiber eccentricity. Once tuned, the fiber holder will remain tuned when removed from the housing, and the high performance connector can be reassembled without loss of tuning.

Description

  This application claims priority of provisional application No. 60 / 636,880 filed on Dec. 20, 2004.

  The present invention relates to an apparatus for making a connection between optical elements, and more particularly to a connector for terminating an optical fiber.

Fiber optic connectors are an integral part of virtually any fiber optic communication system. For example, using such connectors, fiber segments can be joined to make them longer, connect fibers to active elements such as transceivers, detectors, repeaters, etc. Or connected to a passive element. The main function of the fiber optic connector is to align the core of one fiber axially with the core of the other fiber so that all light from one fiber is coupled to the other fiber as efficiently as possible. So that the ends of the two optical fibers are maintained. This is a particularly difficult task because the optical transmission area (core) of the optical fiber is very small. In single mode optical fiber, the core diameter is about 9 microns (1 micron = 1 × 10 ⁻³ mm). For multimode fibers, the core can be as large as 62.5-100 microns, so alignment is less important. However, high-precision alignment is still a necessary function for effectively interconnecting optical fibers.

  Another function of the fiber optic connector is to provide mechanical stability and protection for the bond in its operating environment. The ability to reduce the insertion loss when combining two fibers generally determines the alignment of the fiber ends, the width of the gap between the fiber ends, and the optical surface state of one or both fiber ends. Depends on. Stability and joint protection generally depend on the connector design (eg, minimize the effects of thermal expansion differences and mechanical motion). Fiber optic connectors generally include a small cylindrical member made of metal or ceramic to which a glass or plastic fiber is attached along a central axis. This cylindrical member is generally called a ferrule. The support structure around the ferrule and a mechanism (typically a spring) that presses the ferrule against the mating ferrule includes an operating portion of the optical connector.

  In the connection between a pair of optical fibers, the pair of ferrules abut in an “end-to-end” state, and light travels from one to the other along its common central axis. In this conventional optical connection, in order to minimize the optical loss (insertion loss) caused by the connection, it is highly desirable to align the glass fiber core with high accuracy. However, as expected, it is currently impossible to make a complete connection. Although manufacturing tolerances can be approached to “zero”, practical tolerances such as cost and the fact that slight misalignment can be tolerated may mean that manufacturing tolerances do not necessarily have to be completely zero. Has been suggested. However, what is important in the anticipated operating environment in which the fiber coupling is installed is stability.

  Traditionally, due to manufacturing costs and design features, optical connectors tend to be manufactured as loose component assemblies, many of which are manufactured from plastic. In the case of high performance connectors designed for single mode I applications, there has been a need to eliminate the eccentricity of the assembly, but until the present invention is introduced, all metal or ceramic structures are used. There was no way to use it to achieve tuning and performance in extremely harsh or harsh environments beyond the operating characteristics of plastics. In the past, tuning became effective when the ferrule support structure was engaged with the connector housing. This is undesirable because the housing is an integral part of tuning, and tuning is effectively lost if the housing is removed or replaced.

  One common design for fiber optic connectors is shown in US Pat. No. 4,793,683. Its basic components are a precision molded plastic conical plug centered on an optical fiber, a compression spring disposed around the cylindrical portion of the plug, and a holding that surrounds the plug and spring. It consists of color. The collar includes a male thread that allows it to be coupled to other connectors via a fixture, which has a high precision molded alignment sleeve that can best be represented as a “bicone” shape. Have. This design is shown in U.S. Pat. No. 4,934,785 and has been replaced by a connector comprising a cylindrical plug, a base member holding the plug, a compression spring, and a cap surrounding the plug and spring. . In this design, only the cylindrical plug need only be highly accurate and is generally made from a ceramic material. When joining two of these plugs, an alignment sleeve made from a metal, ceramic or plastic material and consisting of a split thin cylinder is used. This alignment sleeve may not be as accurate as the above-described biconical alignment sleeve.

  Although the connectors described above function well, further improvements were desired. For example, the need for high density interconnecting mechanisms has arisen as optical fibers are increasingly accepted as a choice of transmission media for analog and digital data. All of the aforementioned simplex optical connectors are configured such that the ability to stack a large number of connectors is limited by having to grab both sides by hand when plugging or unplugging it into an outlet or coupling device Has been. Known dual optical connectors as shown in U.S. Pat. No. 4,787,706 must also hold both sides of the housing by hand when unplugging from the outlet or coupling device, so that high density light A fiber interconnect array cannot be constructed.

  Considering these latter demands, looking at the technical field of electrical connectors, the most commonly used and accepted connector in this field is generally the RJ11 type plug used in wired telephone products. / What is known as Jack. These connectors have been widely accepted because they are inexpensive, have high operational reliability, and are easy for customers to understand. However, due to the high accuracy and low insertion loss requirements associated with optical interconnects (especially between small numerical aperture single mode fibers), RJ11 type designs have not been accepted for optical connectors. Examples of such electrical connectors are disclosed in US Pat. Nos. 3,761,869 and 3,954,320.

  Given the technical challenges posed by the alignment of two very small optical fiber cores, it remains desirable to provide a connector that is smaller, cheaper, and more user friendly. Such connectors become extremely commercially important. Such designs are disclosed in U.S. Pat. Nos. 5,481,634, 6,293,710 and 6,287,018, in which plastic materials are used in the manufacture of housing assemblies. Is used. The housing assembly was very similar to the RF11 type described above. The latch system is integrated as a single cantilever assembly. The connector uses a fiber holding structure including a cylindrical plug and a base member that holds an end of the plug. The base member is generally cylindrical but includes a flange surrounding the periphery of one end thereof. A helical helical spring surrounds the base member, one end of the spring pushing the flange and the other end pushing the inner surface of the housing. The ferrule preferably has a circular cross section and its axial passage (capillary) is substantially concentric with the outer cylindrical surface. In addition, the flange is adapted to allow the base member to fit within the housing in a number of different stable positions. Thereby, the deterioration of the optical performance due to the fiber eccentricity can be minimized by rotating the base member to direct the fiber eccentricity in a predetermined direction. In the preferred embodiment of the invention, a square flange is used, but the design feature in the latter patent is that a hexagonal eccentricity adjustment is provided. AT & T Corp. The product descriptions in these patents by Anderson et al. Generally relate to what is known as an LC connector.

  LC connectors are used in optical connector applications except for performance in extremely harsh environments and the ability to tune, i.e., directly inspect internal connectors and replace external components without losing eccentricity compensation. It provides all the functions that are needed for the most part. These are limited by the very nature of the connector itself, i.e. a complex assembly of plastic parts or an integrated outer housing that are unavoidably damaged during repairs. Also, the plastic component is unstable at high temperatures due to its nature, and the plastic component emits gas and becomes brittle. In US Pat. No. 5,481,634, a connector structure using a metal body material is described. However, the proposed design requires a multi-part housing rather than an integral housing. Designed so that such connectors with integral metal or ceramic housing can be manufactured at reasonable cost due to market demand for LC connectors that can withstand harsh environments that maintain tuning, or eccentricity correction If it is possible, it will have extremely high value in various applications such as aerospace, chemistry, and medicine.

  The invention disclosed herein is an optical fiber connector designed for use in harsh environments. The optical connector is configured to have all the features shown below, which are thermal features while maintaining the ability to provide superior optical performance as determined by optical insertion loss and reflection loss performance. And enables operation in harsh environments including mechanical stress. The present invention is a substantially rectangular parallelepiped with a leaf spring latch attached to one of the surfaces. The leaf spring latch is designed to move in an arc with respect to the longitudinal axis of the housing. With the proper design structure, the entire connector housing for harsh environments can be manufactured from metal or ceramic materials. Other materials that do not degrade under thermal and mechanical stress can also be used. Furthermore, when properly integrated with an appropriately designed optical fiber holding structure, the influence of eccentricity can be eliminated from the connector by indexing the fiber holding structure with respect to the rectangular parallelepiped. When properly designed, a metal leaf spring latch system can be used to maintain the connector assembly in a mated state. With this in mind, it is possible to foresee connectors that can operate and repair in extremely harsh environments.

  Several optical fiber connectors are known. Examples of common trade names are FC, SC, ST, and the product most similar to the connector disclosed here is LC. In order to insert and remove these types of connectors, it is generally necessary to allow the user to place a finger on one or more sides of the connector. Connector removal is generally accomplished by sliding the latch (SC), pushing the latch (LC), or rotating the latch (ST, FC). In the case of rotation, the FC connector is a connector that rotates multiple times, while the ST connector is an improvement that requires only partial rotation to decouple the “bayonet” type coupling system. Only the rotating part that separates the connector has metal components. No connector is known which is made entirely of non-plastic (ceramic or metal) components. Moreover, none of the available connector systems that have been identified can be completely disassembled, and fiber eccentricity compensation cannot be maintained when disassembled.

  Thus, the present invention achieves a mounting density that exceeds all identified connectors and achieves a mounting density equal to LC. The latch system is similar to that provided by LC except for the implementation method and manufacturing materials of the latch system. In existing LC connectors, the latch is integrated with the plastic body and is cantilevered. The invention disclosed herein uses a separable “plate” spring type latch system made of a metallic material that is stable to changes in temperature. The unique design features of the disclosed connector allow all plastic materials that can degrade under thermal and mechanical stress to be removed from the connector body, ferrule and support structure as needed. .

  Fiber eccentricity correction is currently only possible with LC type connectors. Said correction is achieved using a square or hexagonal positioning function on the ferrule support structure. The support structure engages with an appropriate pattern in the LC connector body and maintains positioning by engagement with the body. Therefore, tuning, i.e. fiber eccentricity correction, is maintained only when the ferrule and its support are held in the connector body. After removal, the exact positional relationship between the fiber holding structure and the connector body cannot be determined. The invention disclosed herein has an optical ferrule holding structure and support structure with a “key” portion that identifies a position for proper tuning. The invention disclosed herein allows the entire assembly to maintain its eccentricity correction when the fiber support structure is removed from the connector body if this "key" portion is properly positioned and held within the connector body. It shows that you can.

  Since maintaining eccentricity correction is a key feature of the invention disclosed herein, it is important to understand the problem of eccentricity. The variation in alignment between a pair of interconnected ferrules is mainly caused by a parameter known as “eccentricity” of the optical fiber core relative to the ferrule. Eccentricity is defined as the distance between the longitudinal central axis of the ferrule on the ferrule end face and the central axis of the optical fiber core held in the ferrule passage. In general, the passage is not concentric with the outer cylindrical surface, which is the reference surface. Also, the optical fiber may be centered within the ferrule path, and the fiber core may not be concentric with the outer surface of the fiber. Accordingly, the eccentricity consists of the eccentricity of the optical fiber in the ferrule passage and the eccentricity of the passage in the ferrule.

  If you look at the end of an optical fiber that is “passing through”, you can see a circle with a dot of light, which is slightly off the exact center of the circle. Eccentricity can be understood as a two-dimensional vector having a magnitude component and a direction component. The “magnitude component” of the eccentric vector is the linear distance between the center of the circle and the light dot, and the “direction component” of the eccentric vector is the two-dimensional Cartesian coordinate whose origin is the circle center. This is the angle formed with respect to the X axis of the system. The diameter of the ferrule used in the conventional optical connector (that is, ST, SC and FC) is 2.5 mm, but the diameter of the ferrule used in the preferred embodiment of the present invention is LC connection. Note that it is half the size used by the system. By using a smaller size ferrule, the magnitude component of the eccentric vector is reduced proportionally, thereby improving accuracy.

  In general, due to the eccentricity of the optical fiber core relative to the ferrule, rotating one of the two interconnected ferrules changes the relative position of the fiber held in the passage. Since it is extremely difficult to control the eccentricity of the optical fiber core within the ferrule where the optical fiber core is terminated, unless precise tolerances are maintained such that the opposing cores are aligned within about 0.7 microns, It is difficult to achieve a desired loss of 0.1 [dB] or less with a single mode fiber. Of course, this increases the manufacturing cost. If the sum of the eccentricity of the two optical fiber ends to be coupled is the same or at least very close, rotate one ferrule relative to the other ferrule in the alignment sleeve until the maximum coupling (minimum insertion loss) is observed As a result, a low-loss connection can be realized.

  While the invention may be embodied in various forms, it should be understood that the disclosure herein is illustrative of the principles of the invention and is not intended to limit the invention to the illustrated examples. Below, specific embodiments are shown in the drawings and are described in detail herein.

  The structure and method of operation and operation of the present invention, together with further objects and advantages, are best understood by referring to the following description, taken in conjunction with the accompanying drawings, in which like reference numerals designate like elements. it can.

  The present invention can correct for fiber eccentricity by using an indexing structure or portion 90 in the fiber holder structure 50. Although the fiber holder is designed so that the ferrule 44 can be configured to have one of six rotational positions with respect to the index portion 90, the rotational position used is more than this. May be less. With such a design, the ferrule 44 and the fiber holder 50 are indexed to one of six rotational positions (0 degrees, 60 degrees, 120 degrees, 180 degrees, 240 degrees and 300 degrees) and attached to the connector body. be able to. The particular position selected is determined by measuring the fiber eccentricity during connector manufacture and rotating the base member 80 of the fiber holder 50 by an amount determined based on measurements that minimize optical output loss. Is done. The ultimate requirement for a connector with high optical performance is that the ferrule is aligned radially with respect to the key 56 via the index, thereby installing the fiber holder 50 in the connector housing 12. Sometimes this relationship is maintained. For example, the eccentricity is always aligned with the spring latch 30 as shown in FIG. It can be seen how the key 56 engages the housing within the linear slot 24 along one of the housing walls. With the key properly positioned, radial alignment and high optical performance are maintained.

  FIG. 1 shows the assembly of the fiber connector 10 with no fiber cable shown. FIG. 2 shows the basic components of the connector that the operator sees in the field, but without the cable attached. When assembling the connector, the pre-tuned, spring-loaded fiber holder 50 with the cable attached is mounted so that the key 56 slides into the slot 24. 12 is inserted. The positioning cylinder 102 is slid on the rear member 84 and the sliding collar 92 so that the key groove 104 engages with the key 56. To hold the assembly, the threaded collar 100 is positioned over the positioning cylinder 102 so that the threaded collar 100 engages the flange 106 so that the threaded collar 100 engages the flange 106. Screw onto the end 34.

  FIG. 3 discloses further details of the spring loaded index fiber holder 50 for eccentricity correction. The connector includes a housing 12 having an axial passage 14 that terminates at an end surface 16 thereof. This passage is adapted to receive the fiber filament end of a fiber cable (not shown) in the end 42 of the ferrule 44. The housing 12 has an inner surface that defines a cavity 18 that surrounds and houses the fiber holder 50. FIG. 4a shows the housing cavity and fiber holder separated from each other. FIG. 4 b shows the housing cavity 18 surrounding the fiber holder 50. The housing has a first opening 20 that houses a fiber holder 50 to which an optical cable (not shown) is fixed. The housing has a second opening 22 for allowing the end 42 of the ferrule 44 to protrude therethrough. Both openings extend into the cavity 18 and are positioned at both ends of the housing. A manual spring latch 30 is located on one side of the housing to secure the housing to the associated slot (not shown) and prevent them from being accidentally removed. The latch 30 can move in a direction represented by a continuous arc with respect to the longitudinal axis of the fiber holder 50 and has a leaf spring. The latch is permanently or semi-permanently fixed to the housing, and its fixed end 32 is positioned on the second opening 22 side of the housing.

  The connector fiber holder 50 accommodates an optical cable (not shown). The optical cable consists of a glass fiber sealed in a plastic cushioning material. The optical cable further includes a plurality of filamentary reinforcement members that surround the buffered fiber and a plastic jacket that surrounds the filamentary reinforcement members. The optical filament or fiber in the optical cable extends into the axial fiber passage 46 and terminates at the end 42. The fiber path contains a filament that is the end of the strip of the associated fiber cable. The base member 80 holds the ferrule 44. The base member includes an axial optical cable passage 82 that is collinear with the fiber axial passage 46 of the ferrule 44. The diameter of the cylindrical ferrule is about 1.25 millimeters. The shoulder 83 of the base member 80 is engaged with the spring 54. The rear member 84 has a mating portion 86 that is coupled to the rear portion 88 of the base member 80 to form a shaft. The rear member includes a multi-position eccentric index portion 90 such as a hexagonal portion.

  A collar 92 having a shoulder 94 that engages with the spring 54 is also provided. The spring 54 and collar 92 are slidably positioned on the shaft formed by the mating portion 86 and the rear portion 88. The spring member 54 is disposed between the shoulders 83 and 94 and pushes the base member 80 away from the collar 92. This biases the fiber holder toward the second opening 22 so that the end 42 of the ferrule 44 extends through the second opening 22 of the housing. The collar 92 also has a key 56 that engages the slot 24 of the housing 12. This allows the entire fiber holder 50 to be removed from the connector housing and maintains a single stable angular position when returned to the connector housing.

  The housing 12 that houses the fiber holder 50 has an interconnection member or a locking member. This interconnection member or locking member consists of a threaded collar 100 and a positioning cylinder 102. The positioning cylinder 102 has a key groove 104 that engages with the key 56 and pushes the fiber holder 50 toward the second opening 22 of the housing 12. The threaded collar 100 is secured to the housing 12 by engaging the flange 106 on the positioning cylinder 102 around the first opening 20 of the housing and screwing into the threaded end 34. The positioning cylinder 102 slides over a portion of the fiber holder 50 and slides within the cavity 18 of the housing 12. The interconnect member can also have a single metal clip. The metal clip has a plurality of portions fixed to the protrusions on the housing, and engages the key 56 in the same manner as the positioning cylinder.

  The housing and interconnect members are made of a material that does not degrade under extreme thermal or mechanical stress. Such materials include metals and ceramics. The metal material may be an aluminum alloy to make it as light as possible, or it may be a corrosion resistant steel or copper alloy to obtain optimum environmental resistance. Since the housing and the interconnect member are made of a material that, when joined together, substantially surrounds the fiber holder 50 and can withstand extreme thermal and mechanical stresses, The held optical cable is protected.

  The strain relief boot 110 has a longitudinal passage 112 that holds the optical cable. The front portion 114 of the strain relief boot surrounds the rear end 108 of the positioning cylinder 102 and captures the filamentary reinforcing member of the optical cable, whereby the tensile force applied to the optical cable is transmitted to the connector. The strain relief boot is adapted to limit the minimum bend radius of the optical cable in the area where it mates with the connector.

  The cylindrical fiber holder 50 provides a means to “tune” the fiber filament in the ferrule 44 prior to inserting the fiber holder into the housing. This tuning is performed in the fiber holder. Since the indexing structure is accommodated in the fiber holder, the outer surface of the fiber holder 50 can be a cylindrical shape instead of a hexagon. This fiber holder with the indexing component built-in has a cylindrical outer surface so that the housing cavity can be cylindrical rather than hexagonal. Cylindrical cavities can be manufactured more easily from metal or ceramic materials than hexagons. Since the housing is made of a metal or ceramic material, the housing is more resistant to thermal or mechanical stress. Once (just) tuned, the fiber holder will remain tuned even after it has been removed from the housing so that reassembly required for replacement, inspection or cleaning is not lost. It can be carried out. Since the fiber holder is made of a material that can withstand extreme thermal and mechanical stress without losing the tuning position, the connector has very stable optical performance in a wide range of thermal and mechanical environments.

  While the preferred embodiment of the invention has been illustrated and described, those skilled in the art can foresee various modifications may be made without departing from the spirit and scope of the foregoing description and the appended claims. .

It is a figure which shows the fiber connector without a fiber cable. It is a figure which shows the fiber connector assembly without an optical fiber cable before final assembly. It is an exploded view of all the components of an optical fiber connector. It is sectional drawing of the fiber holder and housing before insertion. It is sectional drawing of the fiber holder inserted in the housing.

Claims (11)

An optical fiber connector,
A housing having a body with at least one cylindrical cavity extending longitudinally between opposing first and second ends, wherein the first end is in communication with and located in the cavity A first opening that is aligned, a second end having a second opening that is in communication with and aligned with the cavity, and the housing body includes a first opening from the second end of the housing. A housing having a slot extending toward the end;
A fiber holder having a cylindrical outer surface that can be inserted into the cavity, the ferrule holding a fiber filament therein, a key received in a slot of the housing and including an indexing end A collar, a rear member that includes an indexing portion that can be accommodated within the indexing end and that is complementary to the indexing end, and is disposed between the ferrule and the positioning collar. A fiber holder having a biasing member that biases the indexing end of the positioning collar toward the indexing portion of the rear member;
Means for locking the fiber holder in engagement with the housing body so that the ferrule exits the first opening of the housing.   The housing further includes a flexible latch secured to the outer surface of the housing and engaged with a locking shoulder on the mating connector to hold the fiber optic connector against the mating connector. The optical fiber connector according to 1.   The fiber optic connector of claim 1, wherein the means for locking the fiber holder includes a threaded collar that engages the rear member and is threaded into the threaded end of the housing.   The means for locking the fiber holder further includes a positioning cylinder that slides over the rear member and the collar, the positioning cylinder having a keyway that engages a key on the positioning collar; and 4. The fiber optic connector of claim 3, having a flange engaged by the threaded collar when the collar is screwed into the threaded end of the housing.   The optical fiber connector according to claim 1, wherein a material of the housing is a metal.   The optical fiber connector according to claim 1, wherein a material of the housing is ceramic. An optical fiber connector,
A housing having a body with at least one cylindrical cavity extending longitudinally between opposing first and second ends, wherein the first end is in communication with and located in the cavity A first opening that is aligned, a second end having a second opening that is in communication with and aligned with the cavity, and the housing body includes a first opening from the second end of the housing. A housing having a slot extending toward the end;
A fiber holder having a cylindrical outer surface that can be inserted into the cavity, the ferrule having a fiber passage for holding a fiber filament from the optical fiber cable, and extending on the optical fiber cable and adjacent to the ferrule And a rear member that extends on the fiber cable and includes an indexing portion, the base member and the rear member that is coupled to form the shaft, and slides on the shaft. A positioning collar and a biasing member, the biasing member being disposed between the shoulder portion of the base member and the shoulder portion of the collar, and the positioning collar being engageable with the indexing portion of the rear member. A fiber holder having a key with a leading end and a positioning collar engaging a slot in the housing;
Means for locking the fiber holder in engagement with the housing such that a ferrule comprising the fiber filament exits from the front opening of the housing. An optical fiber connector,
A housing having a body with at least one cylindrical cavity extending longitudinally between opposing first and second ends, wherein the first end is in communication with and located in the cavity A first opening that is aligned, a second end having a second opening that is in communication with and aligned with the cavity, and the housing body includes a first opening from the second end of the housing. A housing having a slot extending toward the end;
A fiber holder having a cylindrical outer surface that can be inserted into the cavity, the ferrule holding a fiber filament therein, and a key fixed to the ferrule and received in the housing slot; ,
Means for locking the fiber holder in engagement with the housing body so that the ferrule exits the first opening of the housing, sliding on a positioning collar, aligned with the key and around the key An optical fiber connector having a positioning cylinder having a keyway that slides on the housing and means for locking including means for fixing the positioning cylinder to the housing.   The optical fiber connector according to claim 8, wherein a keyway of the positioning cylinder engages with a key.   9. The fiber optic connector of claim 8, wherein the means for securing includes a threaded collar that engages a positioning cylinder and is threaded into a threaded end of the housing.   9. The fiber optic connector of claim 8, wherein the key is on a positioning collar secured to a ferrule.

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